Variable-speed power transmission



July 12, 1949. Q L. A. TROFIMOV 2,476,265

VARIABLE S PEED POWER TRANSMI S S ION Filed Sept. 11,1947 3 Sheets-Sheet 1 and Sfaricr July 12, 1949. A. TROFIMOV VARIABLE SPEED POWER TRANSMISSION Filed Sept, '11, I947 3 Sheets-Sheet 2 Sfap S/Drf S e a 55,35, cinfm/ 9 2 a 00. H M06 P w L Y B.

HTTOEIVE) July 12, 1949. 1.. A. TROFlMOV 2,476,266

VARIABLE SPEED POWER TRANSMISSION 3 Sheets-Sheet 3 Filed Sept. 11, 1947 Patented July 12, 1949 2,476,266 VARIABLE-SPEED POWER TRANSMISSION Lev A. Trofimov, Willoughby, Ohio Application September 11, 1947, Serial No. 773,445

17 Claims.

This invention relates to transmissions for driving a power delivery shaft at adjustably variable speed from a continuously running power-supplying motor.

The invention comprises, generally, and among other things, a mechanical power transmission of the differential gearing class, between the power output shaft and a constant-speed power-supplying motor. And a control is provided for the power transmission by which the speed of the output shaft may be adjustably varied between Zero speed and a maximum speed by manual actuation of the control; and by which the speed may be adjustably set by the control to any desired speed in said range from zero to maximum, by manual actuation of the control, and the control will thereafter automatically maintain the set speed constant within a very small, negligible range of variation, regardless of variations of load on the output shaft; and by which when the speed is set as referred to at a selected value, the control may be manually actuated to cause it to automatically bring the speed to zero, and then actuated to increase the speed, and the control will then automatically bring the speed up to the set value.

The entire control is arranged to be operated by manual push button contactors at a central station panel.

It is the primary object of the invention to provide a transmission and control therefor by which the above mentioned speed-control features (among others) of the output shaft, may be accomplished.

Another object is to provide improved means for indicating to an attendant at the control panel the speed of the output shaft at all times whereby he may actuate the control to cause it to effect the desired speed, or speed variations.

Other objects not specifically mentioned, will become apparent upon a reading of the following description which fully discloses the invention, taken in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic view of an apparatus embodying the invention and a control therefor; and showing certain electromagnetic con tactors controlling power circuits thereof and having auxiliary contacts; the circuit connections to the contactor windings and to the auxiliary contacts, being omitted to avoid complications in the drawing;

Figs. 2 to 5 inclusive are diagrammatic views, reproducing the electromagnetic contactors of Fig. 1, with the power circuits omitted, for simplification; and showing the circuit connections to the windings of the contactors and to their auxiliary contacts; and showing manual controls for the contactors;

Fig. 6 is a view illustrating a control panel for the manual controls of Figs. 2 to 5;

Fig. 7 is a diagrammatic view illustrating an embodiment of the invention in another form.

Referring to the drawing, Fig. 1, there is shown at.I a power supplying motor; and it is preferred that it be a constant speed motor, and to this end, I have chosen to illustrate it as a synchronous electric motor, although any other type of engine or motor may be utilized instead. The motor I is energized from three phase supply mains 2 by conductors 3 and 4 through the corresponding main contacts 6 of an electromagnetic contactor 6 having a winding I and auxiliary contacts 8.

The motor I has a direct current field 9 energiZed from the direct current output mains I0 and II of an exciter I2 driven by an alternating current motor I3 connected to the conductors 4 through a transformer and starter I4 of conventional type, whereby the potential of the mains 2 may be different from that required by the motor I3, and whereby the exciter will be started up when the contactor '6 closes.

Field current from the exciter main I0 goes through the winding 9 and back by wires I5I6 to the main I I through a field adjusting rheostat IT. The exciter I2 is self-excited by a field l8.

The exciter I2 also supplies direct current to a pair of fields I9-2II (to be referred to later) the current going from the main I0 by wire 2| through the field l9 and by wire 22 to one end of the resistor 23 of a potentiometer type of rheostat indicated generally at 24; and the current flowing from the wire 2| by Wire 25 through the other field 20 and by wire 26 to the other end of the resistor 23; the currents flowing inwardly through portions of the resistor to an arm 21 movable over the resistor, and thence back to the main I I by wire 28 through the main contacts 2-9 of an electromagnetic contactor 30, having a winding 3| and auxiliary contacts 32.

It will be noted that the field windings I9 and 20 as connected are energized oppositely as to iazgieir polarity; and this is indicated by the arrows At 35 is a differential gearing, comprising a spider 3S, rotatably supporting pinions 31-3! with which mesh differential gears 38 and 39.

The differential gear 39 is connected by a shaft .40 to a gear 4|, meshed with a pinion 42 con- 3 nected by a shaft 43 to the rotor of a direct current generator 44.

At 45 is a differential gearing, comprising a. spider 46 rotatably supporting pinions 41-41 with which mesh differential gears 48 and 49.

The spider 46 is connected by a shaft 50 to a gear 5| meshed with a pinion 52 connected by a shaft 53 tothe rotor of a direct current generator 54. I 7

The differential gear 49 has connected thereto, and rotatable bodily therewith, a gear 55.

The spider 36 is power driven by a gear 56 on the shaft 51 of the motor I; and to this end, the spider 36 may for convenience be in the form of a ring gear having external peripheral teeth meshed with the gear 56.

The gear 55 and therefore the differential gear 49, are power driven at times by a gear 58 on the motor shaft 51 and meshed with the gear 55 and at other times the gear 55 drives the gear 58.

The differential gears 48 and 38 are connected. by shafts 59--60, to worm or helical gears 6 |62, with which are meshed worms or helical gears 63-64, which are connected by a shaft 65. These worm and worm gear sets are alike.

Upon the shaft 65 is a large gear 66, meshed with a smaller gear 61 on a shaft 66 on which also is a larger gear 69, meshed with a smaller gear 10 on a power output load shaft 1| which latter may be connected to any apparatus load to be driven.

The generator 44 has its output terminals connected to the input terminals of the generator 54 by a closed loop circuit comprising wires 12 and I3. I

Certain quantitative features of the apparatus as thus far described will now be given, predicated on a size of apparatus capable of delivering 350 horsepower from the output shaft 11, as an illustrative example.

The motor I may suitably be a 500 horsepower motor running at 1200 revolutions per minute. The generators 54 and 44 may suitably be generators rated at 185 kilowatts at 880 R. P. M.; and the exciter 12 may be of 5 kilowatts capacity. The output shaft 1| and the shafts 59 and 60 and differential gears 46 and 38, are here considered as at rest. The gear'ratio of the gear 56 and spider 36 is one-to-three and the spider is therefore driven at 400 R. P. M.; the differential gear 39 and shaft 40 will therefore be driven at 800 R. P. M. The gear ratio of the gears 4| and 42 is two-to-one so that the shaft 43 and generator rotor 44 are driven at 1600 R. RM.

The gear ratio of the gears 58 and 55 is one-tosix, so that, with the output shaft 1| at rest as here considered, the gear 55 and differential gear 49 are driven at 200 R. P. M.; and the spider 46 and shaft 50 are accordingly driven at 100 R. P. M.

The gear ratio of the gears 5| and 53 is four-toone so that the shaft 53 and rotor of the motor 54 are driven at 400 R. P. M.

The rotors 44 and 54 are driven in the same direction, for example as indicated by the arrows I44 and I43 and as stated at rotary speeds respectively of 1600 and 400.

In the operation of the apparatus thus far described, the motor I and the exciter I2 ar started up by closure of the contactor 6, but it is preferable to do so with the contactor 30 open, to keep the generator fields and I9 unenergized; the synchronous motor field 9 however receiving energization from the exciter.

After the motor I is up to speed, and the gen-- erators 54 and 44 are being driven at.400 and 1600 R. P. M. respectively, the contacto'r is closed and the fields 20 and I9 become energized. There will be degrees of energization for the respective fields 20 and I9 at which the voltage of the generator 54 will be equal to and opposite to that of the generator 44, and, at which no current will flow in the loop 12-43; and it will be assumed that the arm 21 of the potentiometer is at this time in the position to provide these relative field strengths, which may be referred to as normal strengths (although the fields 20 and 19 may not be actually equalized) The generators 54 and 44 therefore will run idly and the whole apparatus will be in an idle condition with the output load shaft 1| at rest.

If new (as by means to be described) the potentiometer arm 21 be moved to strengthen the field l9 and weaken the field 20, the potential of the generator 44 will overpower that of the generator 54 and generate current load in the loop circuit 1213 and supply electric power to the generator 54, and this and the weakened field of the generator 54 will cause it to act as an electrically driven motor.

The load on the generator 44 will cause it to slow down, and the motor-action of the motor 54 will cause it to speed up.

It may be stated as an incidental fact that the interconnected gearing between the generator 44 and motor 5.4 will cause the sum of their speeds to always be equal, in this instance, 2000 R. P. M.

Slowing down of the generator, and with it the differential gear 39, will cause th differential gear 38 to rotate; and speeding up of the motor 54 and with it the spider 46 will cause the difierential gear 48 to rotate inasmuch as the spider 36 and gear 4955 cannot change speed, being geared to the constant speed shaft 51. The rotation of differential gears 38 and 48 will be in the same direction; and they will rotate the worm and worm gear sets 6264 and 6 l63 in the same direction; and the angular or helical direction of the intermeshed teeth of the two worm and worm gear sets being alike, as referred to, they will drive the shaft 65, which, acting through the gears 66 to 10 will drive the output shaft 1| The'adjustment range of the potentiometer 24, and the output of the exciter 12, are provided to be capable of a range of energization of the fields I9 and 20, to cause the generator 44 to be slowed down to 400 R. P. M. and the motor 54 to speed up, acting as a motor,- to 1600 R. P. M.; and corresponding to these speeds, the gear ratio of the gear sets 6l-63 and 62-64, and of the gears 66 to 10 are provided to give to the output shaft the speed of 10,000 R. P. M.

Thus by changing the adjustment at the potentiometer 24 (as will be described) the output shaft 1| may be held at rest, or zero speed; or may be driven at 10,000 R. P. M., or at any intermediate speed, and by very small speed steps, determined by the size of the steps of the potentiometer 24.

As to the power thus transmitted to the output shaft 1|, as its various speeds, it may be said in general, that the generator 44 is in the nature of a reaction point on which the motor I or its shaft 51, reacts, to transmit power through the difierential gearing 35, partly directly to the output shaft and partly to the generator 44; and that the power absorbed by the generator 44 is transformed into electric power at the generator and again transformed into mechanical power at the motor 54 and is transmitted through the differacvaaoe ential earing 4|. partly directly to the output shaft and partly back to the main motor shaft 81. Thus no power is lost except that due to friction and'incidental losses'in the generator and motor 54.

In more detail, the flow of power while driving the output shaft is as follows. Starting with the power supplying motor I, power is supplied by the motor to the shaft 81 and goes thence through gear 88 to thespider I8 and thence to the pinions 81-81 and there divides part flowing to the differential gear 88 and thence to the output shaft H, and part flowing. to the differential gear lland thence to the generator ll to drive it.

From the generator 84. power flows to the motor 84 and thence to the spider 48 and pinions 41-" where it divides, part flowing tothe differential gear 48 and thence to the output shaft H and part flowing tothe differential gear 48 and thence to the motor shaft 81.

Thus the full power of the motor I can be delivered to a load on the output shaft at all speeds. I

Reference has been made to moving the poten tiometer arm 21 to vary the speed of the output shaft. Means will now be described for moving it, under control of an attendant. to automatically adjust the energization of the fields i8 and 28 to cause the output shaft II to rotate at any desired speed in its range, and to maintain that speed at variations of driven load The shaft 65 is extended beyond the worm 84 and connected to the differential gear 12 of a differential gearing I8, having a spider H rotatably supporting pinions ll-18 meshed with the differential gear 12 and with a differential gear 16. A speed reference shaft 11 is connected to the differential gear 18.

The spider 14 has bevel teeth on its periphery meshed with a bevel gear 18 connected to a shaft 19 on which the potentiometer arm 21 is mounted.

The speed reference shaft I1 is driven at different selected speeds (as will be described) and it will be apparent that if its speed is the same as that of the shaft 88, and in the opposite direction, the spider 14 will remain at rest and hold the potentiometer arm 21 at rest; and if the shaft 11 is rotated faster or slower than the shaft 65, the spider will be rotated and rotate the shaft 18 and move the potentiometer arm 21.

The shaft I1 is connected to a differential gear 88 of a differential gearing 8i, comprising a spider 82 rotatably supporting pinions 88-88 meshed with the differential gear 88 and a differential gear 84.

The differential gear 84 is connected to a shaft 85 connected to the rotor of a synchronous motor 88, and to an intermediate variable diameter pulley 81.

The synchronous motor 88 has a direct current field 88 energized by wires 88-48 connected across the exciter i2; and has its stator energized from three phase mains 8| through a magnetic contactor 92 having main contacts 88 and auxiliary contacts 84 and a winding 85.

The pulley 81 is connected by a belt 88 to a like variable diameter pulley wheel 81, on a shaft 98. The pulleys l1 and 81, illustrated as connected by a belt 88, may be and in some cases preferably are, chains and pulleys of the positive drive non-slipping commercial type.

The pulleys and belt are part of a variable speed transmission 88, of a well known type that will be recognized from the simplified showing;

and comprises side levers IOU-ill pivoted at Ill-ill, and engaged at one end with nuts iii-I82, threaded on left hand and right hand threads "8-H" of a rotary screw Ill; and upon rotation of the screw, in one direction or the other, the diameter of one pulley 81 or 81 will be increased and that of the other decreased. in a well known manner.

To rotate the screw I08. it is connected to an induction motor I", energized from three phase mains I81 through the main contacts IOU-488 of magnetic reversing contactors ii8i iIA having respectively windings lll'i i2 and auxiliary contacts "8-4".

The shaft 88 is connected to a gear ill meshed with an idler gear III which in turn is meshed with teeth on the spider 82, and the gear Iii and the spider 82 (as a gear) are of equal diameter. In some cases, it may be preferable for the gear Ill and the spider 82 to be in the form of chain sprockets connected by a chain running thereon.

When the pulleys 81 and 81 are adjusted to equal diameters, or to a 1-to-1 ratio, the differential gear 84 and the spider 82 will rotate at the same speed and in the same direction, as will be apparent; and the differential gear 88 and speed reference shaft 11 will also rotate at that same common speed.

The synchronous motor 86 has a fixed constant speed, and at the said l-to-l ratio of the transmission 89, the speed reference shaft 11 will rotate at the speed of .the motor 86.

If the ratio of the transmission 89 be changed to a 1-to-2 ratio, the spider 82 will be rotated at one half the speed of the differential gear 84, and the speed reference shaft ll will stop rotating. Thus the speed of the speed reference shaft 11 may be adjustably changed from zero speed to the speed of the synchronous motor 88, or any speed in between, by corresponding rotary adjusted positions of the screw I85; and also at any adjusted set speed of the shaft 11, by the screw I85, the shaft 11 may be brought to rest by opening the contactor 82 to stop the synchronous motor 86, without disturbing the adjustment of the screw I85; and upon again closing the contactor 82 and bringing the motor 86 up to speed, the shaft 11 will return to its set speed.

As aforesaid, the shafts l1 and B5 rotate in opposite directions. When therefore the shaft 11 is brought to rest, as aforesaid, and the shaft 65 is turning, the latter will, as described, rotate the shaft 18 and move the potentiometer arm 21- in the said normalizing direction, and this will go on until the fields 20 and is are normalized, and the output shaft II comes to rest, and the shaft 65 stops turning.

For any speed of the shaft 11, if its speed is greater than that of the shaft 65, the shaft 19 will be rotated in the other direction and operate the potentiometer to strengthen field i9 and weaken field 28 and speed up the output shaft II and shaft 65, until the speed of shaft 85, becomes equal to that of shaft Ti, and the output shaft will run at a corresponding speed.

Any slowing down of output shaft H by an increase of driven load, will slow down shaft 65 to a speed less than that of shaft l1, and as will now be clear, teh potentiometer 24 will be operated to speed up the shaft ll again until the shafts 85 and 11 are again of equal speed. The opposite result occurs if the load shaft II and shaft 85 7 speed up due to a decrease of driven load, as will be understood.

Thus in general, the shaft 11 may be.driven at selected constant speeds or brought to rest; and if the two speeds of the shaft 65 and shaft 11 are different. the potentiometer 24 will be operated to speed up or slow down the shaft 65 until they are again equal; and concurrently speed up or slow down the output shaft 1| until said equality is reached.

In general overall operation, the output shaft 1| may be speeded up or slowed down, by turning the screw H in one direction or the other by the reversible motor I06; and brought to a fixed selected speed by momentary rotation of the screw I05. 1| will be attained when the screw I05 has adjusted the transmission 99 to a 1-to-1 ratio.

And the shaft 1| may optionally be brought to rest by stopping the motor 86; or by adjusting the transmission 99 to a 1-to-2 ratio.

The above described control of the speed of the output shaft, embodies the braking principle known as dynamic braking, to quickly stop the output shaft when desired, even if the load driven thereby is a high inertia load which opposes stopping.

Assume the maximum inertia conditions, that is, when the driven load is a high inertia load and the output shaft 1| is rotating at its maximum speed of say 10,000 E. P. M.; and that it is desired to stop the output shaft as quickly as possible; the generator 44 will be running at 400 R. P. M. with full strength of its field l9; and the unit 54 will be operating as a motor at 1600 R. P.

M. with a. minimum strength field; and the potentiometer arm 21 will be in a corresponding extreme position to give these relative fiield strengths.

If now the motor 86 be cut off and stopped, the shaft 11 will stop, and the potentiometer arm 21 will, as described above, move over toward its other extreme position; which will give the'field |9 a weak energization and the field a strong energization.

The motor 54 will then act as a generator at its high speed, and generate high voltage and consequently high current in the loop circuit 12-13. The heavy electrical load on the motor (generator) 54 will rapidly slow it down, and the generator 44 will speed up; and while the stopping of the shaft 11 would in any case as heretofore described ultimately bring the output shaft H to rest, the heavy load as just described on the motor (generator) will bring it quickly to rest, by dynamic braking action.

If, to stop or slow down the output shaft 1|, the shaft 11 were not abruptly stopped by cutting off the motor 86, but were slowed down by rotation of the screw I05 as described, the said dynamic braking action would similarly go into effect but to a lesser degree to aid in slowing down the output shaft 1| The speed of the output shaft may be indicated to an attendant to guide him in operating the motor I06 to turn the screw I05 to effect a desired speed of the output shaft 1|, by any kind of well known tachometer, but I prefer to provide an improved electrically actuated tachometer for this purpose as follows.

Ordinarily, as in prior practice, an electric tachometer instrument is energized by an electric generator driven at the speed of the rotary element whose speed is to be indicated or at a speed proportional thereto.

And the maximum speed of the shaft However, in such tachometers, the speed indicating dial finger (or the like) gives very inaccurate speed indications at the lower speeds, because the tachometer instrument energizing current approaches zero as the indication approaches zero, so that at near zero speeds the energizing current is too small to effect an accurate or reliable indication.

According to my improvement, the tachometer generator is driven by a rotary element of the above described apparatus which not only rotates at speeds commensurably with the speed of the output shaft, (whose speed is being indicated) when the output shaft is rotating, but which continues to rotate after the otuput shaft comes to rest. There is thus always ample generator current to actuate the tachometer instrument even at zero speeds of the output shaft.

In Fig; l, the shaft 98 rotates at the speed of the synchronous motor 86, and at the speed of the speed reference shaft 11, when the ratio of the transmission 99 is 1-to-1. These are the conditions for maximum speed of the output shaft 1|; and under these conditions, a gear I H on the shaft 98 drives a pinion I |8 connected to the tachometer generator H9 and drives it at maximum speed, and develops maximum generator voltage.

When the transmission 99 is changed to its other extreme, to a 1-to-2 ratio, the shaft 98 rotates at one half of its said maximum speed and drives the generator I I9 at half speed and it generates approximately one-half maximum voltage; and this is the condition when the shaft 11 and the output shaft are at rest.

It will be observed that there are other rotary elements'in the system which rotate when the load shaft 1| is at rest, and change in speed commensurably with speed of the load shaft, and which always rotate in one direction, and therefore could be used to drive the tachometer generator H9; among. which are the shafts 43 and 53, for example. A tachometer driven by one of these elements would indicate the speed of the load shaft as it changes. The particular tachometer drive above described (aswill be more fully explained with reference to Fig. 6) responds immediately to a change of setting of the speed ratio of the device 99; and therefore indicates in advance the speed to which the load shaft 1| will arrive when its speed-to-be is adjusted at the device 99; and therefore the operator can, by observing the tachometer. pre-set the speed of the load shaft.

The control for the contactor 6 controlling the main motor of Fig. l to start and stop it are shown in Fig. 2 in a conventional type of diagram.

The contactor 6 is reproduced, as in Fig. 1. The main circuits 3-3 and 4-4 of Fig. 1 are broken off at the contacts 5-5. The winding 1 is connected in a circuit across supply mains |20-|2| through start and stop push button contactors I22 and I23, the contactor I22 being bridged by a maintaining circuit l24--|25 through the auxiliary contacts 9 reproduced from Fig. 1 and which close when the contactor 6 is operated.

A control for the contactor 92 controlling the synchronous motor 86 of Fig. 1 to start and stop it, is shown in Fig. 3 and is like that of Fig. 2, and need not be described, the contactor 92 being reproduced and being under the control of push button contactors |26|21 designated as Speed control on and Speed control off.

A control for the contactor 30 of Fig. 1 to control the field I9 and 20 isshown in Fig. 4 and again is like that of Fig. 2 and neednot be de- 'being under the control of push button contactors III-I20 designated as ,fleldaoni and fields off.

A control for the contactors I Il-I "A of Fig. l to start,'stop,andreverse the motor I and screw I05, is shown in Fig. 5. The contacts Ill-I are reproduced witnthe main motor circuits thereto broken off.

The winding III of contactor H0 is connected across supply mains IIO- -I2I through *the'normally closed interlock contacts II4 of contactor HM, and through anormally open push button contactor ISI.

The winding II! of the contactor IIOA is connected across the mains through the normally closed interlock contacts I ll of contactor I I0 and through a normally openpush button contactor I.

The push button contactors III and I3: are designated as "fast" and slow respectively and are mechanically interlocked bye pivoted lever I34.

In Fig. 3 when-the push button contactor I is momentarily closed, the contactor 02 closes and stays closed and the control of the output shaft speed is under control of the push buttons IOI and I35 of Fig. 5.

Thereafter, when the push button contactor I3I is momentarily closed, the contactor IIO momentarily closes and the motor I00 rotates momentarily and gradually changes the ratio of the transmission 05 to gradually increase the output shaft speed; and when the-desired Speed is at-' tained, the contactor III is opened and the contactor IIO opens and the output shaft runs at that speed.

Similarly, when the push button contactor I is closed, the contactor IIIA operates and the motor I05 runs in the reverse direction to decrease the output shaft speed to a desired slower speed.

In Fig. 3, with the output shaft runningat any set speed as aforesaid, if the push button contactor I2! is opened, the motor 00 of Fig. 1 will stop and the output shaft will come to rest, and if thereafter the push button contactor I26 is momentarily closed, the contactor 02 will operate and stay operated, the motor 05 will again start and come up to speed and the output shaft will resume its set speed.

The push button contactors of Figs. 2 to 5, are all mounted on a central station panel I43 as shown in Fig. 6, with the push buttons designated as in Figs. 2 to 5.

On this panel I45 is mounted alsoa speed indicating instrument, illustrated diagrammatically.

The panel I40 has an arcuate opening I05 therein through which is visible a speed scale dial I36 with speed indications from zero to 10,000 R. P. M.

Behind the panel is an electrically actuated instrument I 01 energized by wires III-400, and of a type having a dial finger I40, which is rotated over the scale to positions commensurate with the degree of energization. The wires "0-400, reproduced from Fig. 1, come from the tachometer generator I I0. The dial finger is conventionally spring returned by a spring I and held against av stop I 4! when the instrument is de-energized. When fully energized at the maximum output of the tachometer generator H0 and maximum output speed of the shaft II, as described, the dial finger I40 will move over and indicate 10,000 R. P. M. When the output shaft is at zero speed, thetachometer generator will be a 10 at half speedanddeliver 50% as much current as at full speed and the dial finger will indicate zero speed on the scale; all for the advantages referred to hereinbefore.

When the operator wants the load shaft to rotate at any desired speed, he operates the device as described tochange its speed ratio, and

asthe speed ratio changes, the tachometer dial finger I40 moves over the scale III; and he ad- Justs the speed ratio until the dial finger indicates the desired speed; and the load shaft comes up motor, and with the generator and motor-connected thereto. trated in Fig. 7.

Shown generally at I44I45 are two differential gearings, the gearing I44 comprising a spider element I46 rotatably supporting a pinion or pin- Such an arrangement is illus- -I ions I41, meshing with differential gearings I40 and I40; and the differential gearing I45 comprising similarly a spider element I50 rotatably supporting a pinion or pinions I5I meshing with differential gears I52 and I50.

In this embodiment of my invention, it is contemplated that the spider elements I45 and I50 are to rotate in opposite directions at equal speeds and to this end are of equal diameter and are provided with gear teeth on their outer peripheries meshed with each other as shown at I54; andin this embodiment of the invention, it is also contemplated that the motor power input is to be at the spiders I45-I50; and accordingly,

2. power supplying, continuously running motor 1 I55 drives a gear I55 meshed with one of the spider elements, for example the spider element I40. The motor I55 may in this case be a squirrel ca e induction motor.

Connected to the differential gears I40 and I49 respectively are gears or pinions I51 and I58, meshed with a gear I50, to which is connected the rotary power outputelement or shaft. here N50.

The differential gears I40-I5I are connected to shafts Nil-I02, which are connected respectively to the rotors or electrodynamic units Its-I64, these units in the operation of the transmission may at one time be a motor and a generator respectively, and at another time agenerator and a motor respectively and preferably are of the direct'current type having respectively field windings l55-I50.

Since the spiders I40-I50 are driven in opposite directions, the torques developed in the shafts IBI and IE2 will be in opposite directions, and this causes torques to be developed in opposite directions in the differential gears I40 and I52. and the gears or pinions I51 and I 55. The differential gears I40 and I4! tend to rotate in the same direction as their associated spider I40, and the differential gears I52 and I55 tend to-rotate uthe same direction as their associated spi In general, with this arrangement, as will be apparent, if little or no torque is required to drive the units Nit-I54 bytheir shafts IOI-I62, they will be driven at equal speeds and at twice the speed of their associated spiders I48--I50;

and the differential gears I45I52 will tend torest, and the output shaft I will remain at rest;

but if one of the units. saythe unit I" is caused to develop ubstantialeleotrical load as a generator, the differential sear Ill will slow dow'npand the differential gear II! will rotate. and more torque will be developed in the diif erential gear I 52 and pinion I58 than in the differential gear 8' and pinion I51, and the pinion I55 will-tiu'n the gear I59 and'the output shaft I50; and the gear I50 will rotate the gear or pinion I51 and the differential. gear I", which will cause the differential gear I" to speed up, and speed up the unit I". As a matter of fact. in a gearing of case the output shaft I80 is drivenflin the other.

direction.

The units I53 and I are always driven in opposite directions, and the shunt windings I 65-456 have suitable polarity. so that the posiare connected together by a wire I51. The other brushes are connected by'a wire I 55. A main circuit is thus provided by the wires ISL-I 88. The shunt field windings I- -I5l are connected respectively at one end to the wire I58 and at their other ends are connected respectively by wires Its-410 to the ends of the resistor "I of apotentiometer rheostat I12, having a rotary contact arm I13 movable over the resistor and connected to the wire I51.

When the units IN-I are running at equal speeds and as generators and have equally energized fields ISIS-I00, their polarities oppose and are equal, and no current flows in the main load circuit ISL-I58. Each generator as shown however, energizes its own shunt field winding through a local circuit across its terminals. The load of this shunt field current develops torque in the shafts ISL-I62 and applies torque to the gears I51 and I58, these torques being equal, and this torque is made suillcient (bysuitable field windings) to load all of the intermeshing gear teeth of the system and eliminate lost motion or backlash therein so that subsequently, as will be described, when one of the torques predominates over the other to start the output shaft I80, from rest, the latter begins to rotate instantly in either the forward or the reverse direction as the case may be without gear tooth backlash or lost motive potentials at the brush terminals of the units' are as indicated in the drawing, and these brushes tion in the gear teeth that supply the driving I torque.

The potentiometer arm I13 obviously will have an intermediate position on the resistor I1I at which the fields I65I68 are equally energized, and at which the potentials of the units I'53I 64 acting as generators are equal and opposed. Movement of the arm I13 from the intermediate position, say toward the left as viewed in the drawing, will strengthen energization of the field winding I86 and weaken that of the field winding I55.

The potential of the unit I acting as a generator will thereby be increased over that of the unit I53. Current will then flow in the said load circuit I81I 58. i

The load current from the generator It will now flow through the unit I", in the direction to operate it as a motor, and because of its weakened shuntfield it will tend to run at a high speed.

At the same time the increased load on, the gen- "erator I54 will cause it itself to slow down.=

. Even if the rotor of the unit I" were'not driven electrically as a motor, it would tend to be driven at increased speed when the rotor of the generator I64 slowed down, because of the said fast that the arithmetical sum of the speeds of the two is alwaysa constant, but, operating electrically as a motor, it tends to run faster-than that speed, and therefore its motor power is given to the shaft IBI and put back into the system, and applied to the output shaft I50 by the gear I51.

Obviously either of the units I53 or I may be caused to operate as a generator; and the other as a motor, by the corresponding movement of the rheostat arm I13 in one direction or the other from its intermediate position, so that as the net result, when the arm I13 is in a certain intermediate position, the output shaft I50 is held at rest by opposed torques; and when moved in one direction, the output shaft will rotate in one direction, and when moved in the other direction the output shaft will run in the other direction. If the arm I13 be movedto slow down the generator I81, the direction of rotation of the shaft I will be determined by the gear I58; and will be determined by the gear I51 if the generator I 50 is the one that is slowed down.

The speed at which the output shaft runs is determined by the extent of movement of the rheostat arm I13 from its intermediate position; and if, with the output shaft I60 running, the rheo'stat arm E13 be returned to its intermediate position, causing the torques applied to the output shaft by the gears I51 and I58 to again become equal and opposite, the output shaft I60 will come to rest. With these two opposing torques on the shaft M5 when at rest, then when one predominates to again turn the shaft I60, all lost motion is already taken up by that torque which increases and predominates, and this is true no matter in which direction, forward or reverse, the shaft turns.

In view of the foregoing. it will be apparent that if the output shaft is connected to an ordinary inertia load' and the load is at rest, the two torques applied to it will be equal and opposite, and lost motion is all taken up in both gearings; and that when one generator (say IE4) is loaded more than the other, the torque of the gear I58 simply increases in magnitude without change of direction to turn the gear I50 and accelerate the load (without introducing gear tooth backlash) and the gear I51 tends to be driven in the directic'ln opposite to that in which its torque is exerted and therefore tends to drive the unit I63 by the gears at a certain increased speed; but the generated load, driving the unit I63 as a motor, drives it above the speed at which it tends to be driven by the gears, and the motor actiontherefore reverses the direction of the gear I51 (which may introduce momentary backlash lost motion in one set of gearing) and thereupon the gear I51 begins to apply torque to the gear I59 and to the load to help drive the load in the same direction as the gear I58 is driving it. But it willbe observed that smooth starting and acceleration of the load without back-lash is not interfered with by the said momentary, backlash of the gear I51, because the load isstarted from rest and driven by the primary torque of the gear I58 which is developed without backlash.

With driven inertia loads the foregoing is true regardless of the direction in which the load is driven. It follows therefore that there is never cessation or interruption of torque on the load shaft I66, in going from rest (zero speed) to speeds in either forward or reverse direction, or in going through zero speed from either direction, or in returning to zero speed.

Again, if the driven load is of an overhauling type of load, (as when the shaft l6 drives a hoist cable drum.) then, when it is at rest, one genera-. tor (say the generator I64) will be loaded more than the other; the gear I66 will be applying I, torque in the direction to hold the load; the

other unit (I63) will be receiving current from the generator I and will be acting as a motor, and exerting torque at the gear I61, which torque also will be in the direction to hold theload. To start and accelerate the overhauling load (or to allow it to overhaul), the generated load of} the generator I66 will be still further increased (or will be decreased) and the torques of the gears I56--I 61 will accordingly both increase in magnitude (or both decrease) without change of direction and therefore without any introduction or back-lash, or any cessation of torques, as the speed of the load changes from, or to, or through zero speed.

The above described operation presupposes that when the output shaft I66 is at rest, the shunt field windings I66 and I66 are equally energized; and that the units I66I6l are running at equal speeds; and that the spiders I66 I56 and gear-s I51-I56 are of equal diameter; and that the two differential gearings Ill-I46 are identical as to gear ratios and diameters; that is to say that the two parts of the system associated respectively with the differential gearings 4-445 are identical and that the transmission as a whole is symmetrical. It is believed to be apparent that the same end result will be obtained with two differential gearings and generator systems which are not identical or symmetrical as the result of differences in the gear diameters and differences in the generators.

It is believed therefore that the fundamental principle of the invention is more generally expressed by saying that certain elements and functions are balanced when the output shaft I66 is at rest, than by saying that they are equal, and this includes balanced energization of the shunt windings I65--I66, balanced potentials and speeds of the generators, and balanced" speeds and torques of the shafts I6I--I62, and balanced torques on the shaft I66 when at rest; and that it is more generally true to say that the balanced torque on the output shaft, when it is at rest, which results from two opposing torques, (or, as in the case of an overhauling type of load and the generator-motor, feed-back principle, results from these torques) eliminates back-lash lost motion by the fact that when the output shaft moves from rest it moves because of a change of the magnitude of the movement effecting torque without change of its direction, whether the movement be from, or to, or through zero speed,

As to the movement of the rheostat arm I13, this may be effected by various means to accomplish various load driving purposes and characteristics, several of which means have been shown in Fig. 7 and either of which may be used optionally.

. is connected a hand wheel I16 for rotating the I66 is connected to a bevel gear I96 meshing with a bevel gear I9I on a shaft I62 to which is connected a hand wheel I93 for turning the shaft.

The shaft I62 extends beyond the hand wheel I93 and has a clutch element I94 splined for axial movement thereon, effected by rocking movement of a lever I96. A corresponding clutch element I96 is connected to the shaft I91 of a motor driven unit I66. The unit I 66 may be any one of the known or commercial units comprising a variable speed transmission, anoutput shaft I61, and a motor I69 for driving the output shaft through the transmission, and the transmission being provided with adjustable means for varying and setting the speed of the output shaft I61, and for maintaining it constantly at any set speed, in either the forward or reverse direction. The transmission I96 illustrated is provided with a hand wheel 266 for adjusting the speed of the output shaft I66, and a dial and scale 26I for indicating direction and speed, at which it is set, and the motor I96 for driving it.

Assuming that the driven load connected to the output shaft I66 is one whose speed and direction is to be controlled by hand, the clutch I94I66 is first disconnected by operating the lever I65. The hand wheel I16 is then turned, turning the shaft I11, and this as will be apparent, acting through the worm I16 and worm gear I15, will move the arm I13 over the resistor I1I in one direction or the other from its intermediate point, to cause the output shaft I66 to rotate in one direction or the other, and at a speed proportional to the extent of movement of the arm I13. To stop the output shaft from rotating the arm I13 may be rotated back to its intermediate point by the hand wheel I16.

For any position of the arm I13, the output shaft will tend to rotate at a corresponding speed. To bring the load to rest the hand wheel I16 is turned to move the arm I13, to its intermediate position of balance. The load can thus be driven in the forward direction or the reverse direction at different speeds, or brought to rest by the hand wheel I16. For overhauling loads the arm I13 would be stopped at one side of its middle position, as will be understood.

During this control, and referring to the differential gearing I63, the differential gear I66 will be rotated, and rotate the differential gear I and the gear I9I and the hand wheel I63, idly; but the shaft I6I will not be driven, thereby. The shaft I6I will be rotated idly byv the hand wheel I16. 0

Again, if the load on the output shaft I66 is one which it is desired to drive accurately at a constant preselected speed, then the clutch ISL-I96 would be engaged by the lever I65, and the hand wheel 266 would be turned to set the transmission I96 to drive its output shaft I61 at a set constant speed. 7

It may be assumed here for simplicity, that the output shaft I66 is at rest, and that the rheostat arm I13 isin its said intermediate position of balance. The transmission I98 now rotates the shaft I92, gears ISM-I90 and the differential gear I85. The differential gear I88 is at rest and the gear I85 turns the spider I82, and the shaft I8I, and the gears I80I19, and the shaft I11, thereby moving the rheostat arm I13 over the resistor, causing the output shaft I80 to rotate, at increasing speed. This rotational movement of the shaft I80, acting through the idler I89 and the gear I88 and shaft I81, turns the differential gear I88 in the direction opposite to the direction of the differential gear I85, and the increasing speed of the gear I88 brings it up to a speed at which it equals that of the gear I85; and thereupon the spider I82 stops rotating and stops movement of the arm I13, and the output shaft I80 thereafter rotates at the speed which it has by this time attained. If the output shaft I80 should, because of an increase of load thereon, tend to slow down, it will slow down rotation of the differential gear I88; and the gear I85, rotating at its constant speed will rotate the spider I82 and cause the arm I13 to be moved on the resistor to bring the speed of the output shaft back again to its preselected speed. Any tendency of the output shaft to increase in speed, is correspondingly corrected by movement of the rheostat arm I13 in the other direction by a simil ar response of the differential gearing I83.

The speed of rotation of the output shaft can at any time be set to a different constant speed by operation of the hand wheel 200 of the transmission I98.

During thisregulation the hand wheel I18 will rotate idly as will the hand wheel I93.

In this connection it should be observed that the motor driven transmission unit I98 may be of very small fractional horsepower, incapable of driving by itself the load of the output shaft I80, whereas the motor I55 and the output shaft I86 and the associated elements of the transmission may be of large size able to transmit great horsepower, theunit I98 being merely a speed reference unit having only enough power to operate the rheostat arm I13.

Again, in some cases, the output shaft I80 willbe connected to a driven load which is to be moved to a desired position and left in that position. Illustrative of such uses is the aiming of guns by motor power. In such a case, the output shaft I80 is to be rotated, preferably at high speed for a number of revolutions and then automatically slowed down and stopped. To effect this control, the clutch I94I98 is disengaged and the hand wheel I93 is turned. This turns the gear I85, and the spider I82 and the shaft I8I and moves the rheostat arm I13 to cause the output shaft to rotate.

Rotation of the output shaft turns the gears I88 and I88 in the direction to tend to neutralize,-

the effect of rotation of the gear I85. Thus, so to speak, the differential gear I88 tries to catch up with the gear I85. The faster the wheel I93 is turned the more will the speed of the gear I85 stay ahead of the gear I88 and keep the rheostat arm I13 moving farther and farther from its midposition. There is a speed of rotation for the wheel I93 at which the arm I13 will become stationary on the resistor HI, and cause the output shaft to have a corresponding speed. If the rotation of the hand wheel I93 is slowed down below that speed or is stopped altogether, then the speed of the gear I88 will catch up with and overcome the speed of the gear I85, and turn the shaft I8I in the other direction, to return the arm I13 back 16 toward its position of balance, slowing down the output shaft I80, and when the arm reaches the position of balance the output shaft will stop rotating.

During this control the hand wheel I18 rotates idly.

In the case of control by the hand wheels I18 or I83, the load, whether it is an overhauling load (as when the shaft I drives a hoist cable drum) or whether it is one .moving with reat inertia, improved dynamic braking may be had by the transmission.

Movement of the rheostat arm I13 controls the direction of torque on the output shaft I80 independently of the speed or direction of the output shaft. To quickly brake or stop an overhauling load or a load of great inertia, the rheostat arm I13 may be moved to a position which tion so as to maintain a load holding torque (if' if be an overhauling load). As much torque as desired may thus be applied to brake the load, from high speed all the way to zero speed; and in fact, if the braking torque thus developed is not removed by return movement of the arm I13 when the load is brought to rest, it will immediately reverse the load under full power and torque; and this latter action, which is sometimes wanted, corresponds to the action obtained with conventional motor controls and is known as plugging the motor.

No additional elements are required to provide such dynamic braking or "plugging with the transmission above described.

The transmission may be controlled by the hand wheel I93 as above referred to, to effect the driving of loads in the forward or reverse direction at different speeds, or to bring it to rest, instead of by the hand wheel I18, and when so doing, an additional feature of control may be had to advantage. Upon turning the hand wheel I 93, (assuming for the sake of simplicity that the load is at rest), the shaft I8I moves the arm I13 to start the output shaft I80 as described. This starts rotation of the differential gear I88. The hand wheel l93 may be turned at a sufficiently rapid speed so as to cause the arm I13 to be moved a corresponding distance alon the resistor I1I before the differential gear I86 catches up with the differential gear I85, 50 that the output shaft may be caused to attain a desired speed. If not the hand wheel I83 be released, the rheostat arm I13 will stay in its moved position for that speed of the output shaft, and the rotating differential gear I88 will retate the gear I85, and, through the gears I90-I9I., will cause the hand wheel I93 to continue to rotate idly. The output shaft therefore will continue to be driven at its desired speed. To bring the load to rest, the hand wheel I 93 may be grasped and its rotation stopped. The rotating gear I88 will now rotate the spider I82 to restore the arm I13 in the other direction to its intermediate position at which the output shaft will come to rest. If, instead of merely stopping the hand wheel I93. it be rotated in the opposite direction, the arm I13 will be restored more rapidly to more rapidly stop the load, or if the hand wheel I93be turned fast enough and far enough in the op osite direction,

the arm I'll will move beyond its intermediate the gear I It; and'to have the same output speed position and stop the load by the plugging action may be used alone; or any of them in combination with another; the reason for illustrating and describing all of them in connection with the embodiment of Fig. 7 being to simplify the drawing which otherwise would require numerous additional figures.

While the fields I85.-I80 are in Fig. 7 energized by the units I63-'-I6| themselves, to always load these units for the advantages described, these fields may be energized from an independent source, for example as in Fig. 1.

When as in the form of Fig. 1, the speed of the output shaft II is varied in a speed range from zero to maximum, but always in the same direction, I have found that an increase in gearing transmission efilciency as well as other advantages, is effected, if the'speed of the shaft 40 is maximum and the speed of the shaft 50 is at a corresponding minimum when the load shaft II is at rest; due to the fact that the maximum peripheral speeds of the tooth-engaged gears of the differential gearings 35-45 will then be the least for the whole range of load shaft speed; and this is effected by the disclosed arrangement of the gears of the respective gearings 35-45, whereby one is power-driven by its spider 30, and the other by its differential gear 49.

When, as in Fig. '7, the speed of-the load shaft I60 is varied from zero to a maximum speed in each direction, I have found that the gearing transmission emcien cy is greatest when the two range as for Fig. 7, the speed of the input sear III in this hypothetical arrangement would have to be twice that of the speed of the input spider III of Fig. 7.

The peripheral speeds of the-gears at their gear tooth engagement, particularl that oi the pinions III-III (which in practice are usually much smaller in diameter than the differential gears) would be excessive in either of these hypothetical' cases. with resulting inefiiciency.

The said pinions rotate due to relative speed between the differential gears and the spider.

This relative speed, at its maximum in Fig. 7, is two to one. In the second hypothetical case above it is twice as great as that; and in the first hypothetical case is four times'as great.

Subject matter illustrated and described herein but not claimed is being claimed in my copending application, Serial No. 96,372, filed May differential gearings I44 and I45 have their respective groups of three gear elements homologously arranged; and when the power is put in at say the spider element I and taken out at say the difierental gear I52 as described. This may be made clear as follows.

In Fig. 7, for a given speed of the input spider I50, and with the output gear I52 at rest, the speed control gear I 53 has twice the speed of the iput spider I50. Upon slowing down the gear I 53 (by the control and theoretically to zero) the speed of the output gear I52 goes up to double that of the input spider I50.

For the same gearing and same delivered speeds and same power input speed as in Fig. 7, if, hypothetically, the power were for example put in at the gear I53 and taken out at the spider I 50, and the speed of the gear I52 were varied (by the 'control), then when the output spider I50 was at rest, the control gear I52 would rotate at the same speed as the input gear I53. When the speed of the gear I52 was reduced (by the control and theoretically to zero) the speed of the output spider I50 would rise-to only one-half of the speed of the input gear I53.

With this hypothetical arrangement, therefore, to have the same output speed range for the output spider I50 as that of the output gear I52 of Fig. 7, the speed of the input gear I53 in this arrangement would have to be four times as great as that of the input spider I50 of Fig. 7.

. Again, if, for example, and hypothetically, the power were put in at the gear I53 and taken out at the gear I52, and the speed of the spider I50 were varied (by the control), then when the gear I52 was at rest, the spider I50 would rotate at one-half the speed of the gear I 53. When the speed of the spider I50 was reduced (by the control and theoretically to zero) the speed of-the output gear I52 would rise only to the speed of I claim:

1. In a power transmission for driving a power output load shaft at variable speed; a first and a second diirerential gearing, each comprising three elements, namely, a spider rotatably supporting a pinion and a pair of differential gears meshed with the pinion; one difi'erential gear of each gearing connected to the load shaft and both driving it; the spider of the first gearing and the other diflerential gear of the second gearing adapted to be drivingly connected to a continuously running power supplying motor; an electric generator driven by the'other differential gear of the first gearing; an electric motor receiving current from the generator and driven thereby and 'drivingly connected to the spider of weaken that of the motor.

2. In a power transmission for driving a power output load shaft at variable speed; a first and a second diiIerential gearing, each comprising three elements, namely, a spider rotatably supporting a pinion and a pair of difierential gears meshed with the pinion; one difierential gear of each gearing connected to the load shaft and both driving it; the spider of the first gearing and the other difierential gear of the second gearing adapted to be drivingly connected to a continuously running power supplying motor; an electric generator driven by the other difierential gear of the first gearing; an electric motor receiving current from the generator and driven thereby and drivingly connected to the spider "of the second gearing to drive it; the generator and motor having field windings; circuit means supplying current to the field windings; and field current controlling means for increasing the field strength of the generator sufficiently to cause it to develop increased electrical load sufllciently to slow it down, and increase the speed of the motor by the increased generator current supplied thereto, and to concurrently weaken the strength of the motor field suillcientl to further increase its speed to thereby cause the said one diflerential gear of both gearings to increase in speed and increase the speed of the load shaft.

3. In a power transmission for driving a power output load shaft at variable speed; a first and a second differential gearing, each comprising 19 three elements, namely, a spider rotatably supporting a pinion and a pair of differential gears meshed with the pinion; one diiferential gear of each gearing connected torthe load shaft and both driving it; the spider of the first gearing and the other difierential gear of the second gearing adapted to be drivingly connected to a continuously running power supplying motor; an electric generator driven by the other diflerential gear of the first gearing; an electric motor receiving current from the generator and driven thereby and connected to the spider of the second gearing to drive it; the generator and motor havin field windings; circuit means supply ng current to the field windings; and current controlling means for varying relatively the current to the field windings, to concurrently increase the field strength of the generator and weaken that of the motor; to develop increased electrical load on the generator and thereby to slow it down, I

-ierential gear of both gearings to increase in speed and increase the speed of the load shalt;

; the fields having relative strengths at which the said one difierential gear of both gearings are at rest and the load shaft is at rest.

4. In a power transmission for driving a power ,output load shaft at variable speed; a first and a second difierential gearing, each comprising three elements, namely, a spider rotatably supporting a pinion and a pair of difierential gears meshed with the pinion; one differential gear of each gearing connected to the load shaft and both driving it; one of the other two elements of each gearing adapted to be drivingiy connected to a continuously runnin power supplying motor; an electric generator drivenby the third element of one gearing; an electric motor; the generator and motor having energizable fields; a circuit supplying current developed by the generator to the motor and driving it; the motor I connected to the third element of the other gearing and driving it; a field energizin circuit and control means to relatively vary the respective field strengths; the fields having relative strengths at which the electrical load developed by the generator slows it down, and the electric load supplied by the generator to the motor speeds it up, and the said one diiferential gear of the respective gearings drive the load shaft; and the fields having other relative strengths at which the generator speeds up to a maximum speed and the motor slows down to a minimum speed slower than the maximum speed of the generator at which speeds the load shaft is at rest.

5. In a power transmission for driving a power output load shaft at variable speed; a first and a second differential gearing, each comprising three elements, namely, a spider rotatably supporting a pinion and a pair of difierential gears meshed with the pinion; one differential gear of each gearing connected to the load shaft and both driving it; one of the other two elements of each gearing adapted to be drivingly connected to a continuously running power supplying motor; an electric generator driven by the third element of one gearing; an electric motor; the generator and motor having energizable fields; a circuit supplying current developed by the generator to the motor and driving it; the motor connected to the third element of the other gearing and driving it; a field energizing circuit and control means the fields having relative strengths at which the electrical load developed by the generator slows it down, and the. electric load supplied by the generator to the motor speeds it up, and the said one difierentlal gear or [the respective gearings drive the load shaft; and having other relative strengths at which the counter voltage of the motor balances the generator voltage, and the motor is driven by the thirdearing element to which it is connected, and the said one difi'erentiai gear or the respective gearings are at rest and the load shaft is at rest; and the generator has a maximum speed and the motor a minimum speed less than the generator maximum speed.

6. In a power transmission for driving a power output load shait at variable speed; a first and a second difi'erentiai gearing each comprising three elements, namely, a spider rotatably supporting a pinion. and two differential gears meshed with the pinion; one element of each gearing adapted to be drivingly connected to a continuously running power supplying motor, a second element of each gearing drivingly connected to the load shait; a generator driven by the third element of the first gearing; a motor drivingly connected to the third element of the second gearing; the motor electrically connected to the generator and being driven by its current load; the motor and generator having variably energizable fields; an energizing circuit for the fields and rotary circuit control means for varying the strengths of the fields to selectively increase one and decrease the other and vice verse; to cause the generator to slow down and the motor to speed up and vice versa and thereby cause the load shaft to be driven at different selected speeds; a first and a second control difierential gearing each comprising three elements namely a spider rotatably supporting a pinion and two difierential gears meshed with the pinion; means driving one element of the first control gearing at a speed proportional to the load shalt speed; and a second element drivingly connected to the rotary circuit control means; and its third element drivingly connected to an element of the second control gearing; a variable speed ratio transmission comprising a rotary driving input element and a rotary driven output element and operable adjusting means for varying the speed ratio therebetween; a constant speed motor driving the input element; the other two elements of the second control gearing drivingly connected respectively to the input and output elements.

7. In a power transmission for driving a power output load shaft at variable speed; a first and a second diflerential gearing each comprising three elements, namely. a spider rotatably supporting a pinion, and two differential gears meshed with the pinion; a spider of the first gearing and a differential gear of the second gearing, adapted to be drivingly connected to a continuously running power supplying motor, a diilerential gear of each gearing drivingly connected to the load shaft; a. generator driven by the other differential gear or the first gearing; a motor drivingly connected to the spider of the second gearing; the motor being driven by current load of the generator; the motor and generator having variably energizable fields; an energizing circuit for the fields and circuit control means for varying the strengths of the fields to increase one and decrease the other and vice verse; to cause the generator to slow down and the motor to speed to relatively vary the respective field strengths; is up and vice versa to thereby cause the load shaft to be driven at a corresponding speed; and the' fields having relative strengths at which the generator is driven at maximum speed and the motor at minimum speed less than the generator maximum speed and at which speeds theload shaft is at rest.

8. In a power transmission for driving a power output load shaft at variable speed; a first and a second differential gearing each comprising three elements, namely, 'a spider rotatably supporting a pinion, and two differential gears meshed with the pinion; one element of each gearing adapted the fields to selectively increase one and decrease the other and vice versa; to cause the generator to slow down and the motor to speed up and vice versa and thereby cause the load shaft to be driven at different selected speeds; a first and a second control difierential gearing each comprising three elements namely a spider rotatably supporting a pinion and two differential gears meshed with the pinion; meansdriving one element of the first control gearing at a speed proportional to the load shaft speed; and a second element drivingly connected to the rotary circuit control means; and its third element drivingly connected to an element of the second control gearing; a variable speed ratio transmission comprising a rotary driving input element and a rotary driven output element and operable ad-- just-lug means for varying the speed ratio therebetween; a constant speed motor driving the' input element; the other two elements of the second control gearing drivingly connected respectively to the input'and output elements; the

variable speed ratio transmission having a speedratio at which the connected elements of the first and second control gearings remain at rest,

and other different ratios at which said connected elements rotate at respectively different speeds.

9. In a power transmission for driving a power output load shaft at variable speed; a first and a second differential gearing each comprising three elements, namely, a spider rotatably supporting a pinion, and two differential gears meshed with the pinion; one element of each gearing adapted to be drivingly connected to a continuously runnin power supplying motor, a second element of each gearing drivingly connected to the load shaft; a generator driven by the third element of the first gearing; a motor drivingly connected to the third element of the second gearing; the motor electrically connected to thegenerator and being driven by its current load; the motor and generator having variably energizable fields; an energizing circuit for the fields and rotary circuit control means for varying the strengths of the fields to selectively increase one and decrease the other and vice versa; to cause the generator to slow down and the motor to speed up and vice versa and thereby cause the load shaft to be driven at different selected speeds; a first and a second control differential gearing each comprising three elements namely a spider rotatably portional to the load shaft speed; and a second element drivingly connected to the rotary circuit control means; and its third element drivingly connected to an element of the second control gearing; a variable speed ratio transmission comprising a rotary driving input element and a rotary driven output element and operable adjusting means for varying the speed ratio therebetween; a constant speed motor driving the input element; the other two elements of the second control gearing drivingly connected respectively to the input and output elements; and operable means to start and stop the constant speed motor at any speed ratio adjustment.

10. In a power transmission for driving a power output load shaft at variable speed; a first and a second differential gearing each comprising three elements, namely, a spider rotatabl supporting a pinion, and two differential gears meshed with the pinion; one element of each gearing adapted to be drivingly connected to a continuously running power supplying motor, a second element of each gearin drivingly connected to the load shaft; a generator driven by the third element of the first gearing; a motor drivingly connected to the third element of the second gearing; the motor electrically connected to the generator and being driven by its current load; the motor and generator having variably energizable fields; an energizing circuit for the fields and rotar circuit control means for varying the strengths of the fields to selectively increase one and decrease the other and vice versa; to cause the generator to slow down and the motor to speed up and vice versa and thereby.cause the load shaft to be driven at different selected speeds; a first and a second control differential gearing each comprising three elements namely a spider rotatably supporting a pinion and two differential gears meshed with the pinion; means driving one element of the first control gearin at a speed proportional to the load shaft speed; and a second element drivingly connected to the rotary circuit control means; and its third element drivingly connected to an element of the second control gearing; a variable speed ratio transmission comprising a rotary driving input element and a rotary driven output element and operable adjusting means for varying the speed ratio therebetween; a constant speed motor driving the input element; the other two elements of the second control gearing drivingl connected respectively to the input and output elements; the variable speed ratio transmission having a speedratio at which the connected elements of the first and second control gearings remain at rest, and other different ratios at which said connected elements'rotate at respectively different speeds; and a tachometer instrument energizing generator driven at speeds proportional to the speeds of the said output element at different speed ratio adjustments.

11. In a power transmission for driving a power output load shaft at variable speed; a first anda second differential gearing each comprising three elements, namely, a spider rotatably supporting a pinion, and two differential gears meshed with the pinion; one element of each gearing adapted to be drivingly connected to a continuously running power supplying motor, a second element of each gearing drivingly connected to the load shaft; a generator driven by the third element of 23 the first gearing; a motor drivin'gly connected to the third element of the second gearing; the motorelectrically connected to the generator and being driven by its current load; the motor and generator having variably energizable fields; an energizing circuit for the fields and rotary circuit control means for varying the strengths of the fields to selectively increase one and decrease the other and vice verse; to cause the generator to slow down and the motor to speed up and vice versa and thereby cause the load shaft to be driven at different selected speeds; a first and a second control differential gearing each comprising three elements namely a spider rotatably supporting a pinion and two differential gears meshed with the pinion; means driving one element of the first control gearing at a speed proportional to the load shaft speed; and a second element drivingiy connected to the rotary circuit control means; the second control gearing having one differential gear drivingly connected to the third gearelement of the first control gearing; a variable speed ratio transmission comprising a rotary driving input element and a rotary driven output element and operable adjusting means for varying the speed ratio therebetween; a constant speed motor driving the input element; the second control gearing having its other differential gear drivingly connected to the input element, and having its spider driven by the output element and in the same direction and at a one-to-one speed ratio; the variable speed ratio transmission when at a one-to-two ratio between the input and output elements, causing the connected differential gears of the two control gearings to remain at rest, and at more nearly equal ratios causing them to rotate.

12. In a power transmission fordriving a power output load shaft at variable speed; a transmission mechanism comprising a pair of differential gearings each gearing comprising three elements, namely: a spider rotatively supporting a pinion and two differential gears meshed with the pinion; one element of each gearing drivingly connected to the load shaft; another element of each gearing adapted to be drivingly connected to ,a continuously running power supplying motor; the third elements of the gearings drivingly connected respectively to an electric generator and an electric motor, having respective field windings; the motor electrically connected to the generator to be electrically driven thereby; an electric circuit for energizing the field windings, and rotary circuit control means controlling the current in the windings to vary the field strengths relatively; to cause the generator to slow and the motor to speed up and vice versa, and thereby cause the load shaft to be driven at corresponding speeds; at three element control differential gearing; means to drive a first element of the control gearing at speed commensurable with the speed of the load shaft, and a second element of the control gearing connected to the rotary control means to drive it; a constant speed control motor; a variable-speed-ratio transmission device between the control motor and the third element of the control differential gearing, and thereb rendered effective to hold the rotary control means at rest at a predetermined speed ratio of the device and to cause it to rotate at other speed ratios; and operable means to change the speed ratio of the variable-speedratio device.

13. In a power transmission for driving a power output load shaft at variable speed; a transmission mechanism comprising a" pair of differential gearings each gearing comprising three elements, namely: a spider rotatively supporting a pinion and two differential gears meshed with the pinion; one diflerential gear of each gearing connected to the load shaft; the spiders of both gearings adapted to be connected to a continuously running power supplying motor to'be driven thereby; an electric generator and an electric motor connected respectively to the other differential gears of the gearings; the motor electrical- 1y connected to the generator to receive current therefrom and be electrically driven thereby; the

motor and generator-having respective field windings; circuit means supplying current to the field windings; and circuit controlling means for varying relatively the current to the field windings to concurrently relatively strengthen one and weaken the other.

14. In a power transmission for driving a power output load shaft at variable speed; a transmission mechanism comprising a pair of differential gearings each gearing comprising three elements, namely: a spider rotatively supporting a pinion and two differential gears meshed with the pinion; one differential gear of said gearing drivingly connected to the load shaft; the spiders of both gearings adapted to be connected to a continuously running power supplying motor to be driven thereby; an electric generator and an electric motor connected respectively to the other differential gears of the gearings; the motor electrically connected to the generator to receive current therefrom and be electricall driven thereby; the motor and generator having respective field windings; circuit means supplying cur rent to the field windings; and rotary circuit controlling means for varying relatively the current to the field windings to concurrently relatively strengthen one and weaken the other; to cause the generator to slow down and the motor to speed up and vice versa to thereby cause the load shaft to be driven at corresponding speeds; a three element control differential gearing; means driving one element of the control gearing at speed proportional to that of the load shaft; another element of the control gearing being connected to the rotary circuit controlling means; a variable speed ratio transmission device having a rotary input and a rotary output element; the output element connected to the third element of the control differential gearing; a constant speed motor driving the input element of the device; and operable means to change the speed ratio of the device.

15. In a power transmission for driving a power output load shaft at variable speed; a transmission mechanism comprising a pair of differential gearings each gearing comprising three elements, namely: a spider rotatively supporting a pinion and two differential gears meshed with the pinion; one differential gear of each gearing drivingly connected to the load shaft; the spiders of both gearings adapted to be connected to a continuously running power supplying motor to be driven thereby; an electric generator and an electric motor connected respectively to the other differential gears of the gearings; the motor electrically connected to the generator to receive current therefrom and be electrically driven thereby; the motor and generator having respective field windings; circuit means supplying current to the field windings; and rotary circuit controlling means for varyin relatively the current to the field windings to concurrently relatively strengthen one and weaken the other; to cause the generator to slow down and the motor to speed up and vice verse to thereby cause the load shaft to be driven at corresponding speeds; a three element control diiferential gearing; means driving one element of the control gearing at speed proportional to that of the load shaft; another element of the control gearing being connected to the rotary circuit controlling means; a variable speed ratio transmission device having a rotary input and a rotary output element; the output element connected to the third element of the control differential gearing; a constant speed motor driving the input element of the device; and operable means to change the speed ratio of the device; a disconnecting clutch between the third element of the control differential gearing and the device; a handle for rotating the third element of the control gearing; and a handle for rotating the rotar current control means.

16. In a power transmission for drivin a power output load shaft at variable speed; a transmission mechanism comprising a pair of' differential gearings each gearing comprising three elements, namely: a spider rotatively supporting a pinion and two difierential gears meshed with the pinion; one element of each gearing connected to the load shaft; another element of each gearing adapted to be drivingly connected to a continuously runnin power supplying motor; the third elements of the gearings connected respectively to an electric generator and an electric motor, having respective field windings; the motor electrically connected to the generator to be electrically driven thereby; an electric circuit for energizing the field windings, and rotary circuit control means controlling the current in the windings to vary the field strengths relatively; to thereby cause the generator to slow down and the motor to speed up and vice versa to cause the load shaft to be driven at a corresponding speed; a control differential gearing; means driving a first element of the control gearing at speed commensurable with the speed of the load shaft and a second element of. the control gearing being connected to the rotary control means to drive it; a constant speed control motor; a variable-speed-ratio transmission device between the control motor and the third element of the control differential gearing, and thereby rendered effective to hold the rotary control means at rest at a predetermined speed ratio of the device and to cause it to rotate at other speed ratios; and operable means to change the speed ratio of the variable-speed-ratio device.

17. In a power transmission for driving a power output load shaft; a continuously running power supplying motor; differential transmission gearing between the motor and the load shaft; a transmission controller comprising a continuously rotatable element and means responsive to change of speed of the rotatable element to initiate a gradual change of the relative speeds of the differential gears and a gradual change of the speed of the output shaft to an ultimate attained speed; a source of power and a variable speed-ratio transmission device for rotating the rotatable element at different speeds; operable means to adjustably change the speed ratio of the device to change the speed of the rotatable element and thereby preset the speed which the output shaft will attain; and a tachometer driven at a speed proportional to that of the rotatable element and indicating the preset .speed which the output shaft will attain.

LEV A. TROF'IMOV.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,348,211 Frische et al Ma 9, 1944 2,384,776 Troflmov Sept. 11, 1945 2,429,570 Trofimov Oct. 21, 1947 

